The structural chemistry of titanyl oligomers and polymers

Abstract

Chain-like and cyclic structures of compounds with a ⋯Ti–O–Ti–O⋯ backbone are reviewed, that is, compounds in which the coordination octahedra of the titanium atoms share corners by means of μ2-O atoms. The charge of the TiO2+ unit is balanced by organic or inorganic ligands which additionally complete the coordination sphere of the titanium atoms. Typical substitution patterns are two mono-anionic bidentate ligands, two monodentate anionic plus two neutral ligands, or one tetradentate dianionic ligand. While only few examples of polymeric chain structures, or segments thereof, were structurally characterized, several types of cyclic compounds are known. This includes rings in which the Ti polyhedra are only linked via the μ2-O atoms, capped rings, or rings in which the titanium octahedra are additionally bridged by organic ligands.